The present invention relates to a method of preventing damage to an immersed tuyere of a decarburizing furnace or a converter for use in an oxygen steel making process. More specifically, the invention is concerned with a method of preventing, the damage to an immersed tuyere often experienced during the steel making process in the oxygen steel making process in which molten pig iron is decarburized and refined into steel, by injecting a particulate agent together with a carrier gas into the molten pig iron.